Vegetation pruning device

ABSTRACT

A vegetation pruning device ( 102 ) includes a pair ( 114, 116 ) of pivotably coupled handles and a motor having a rotary output drive ( 130 ) for driving an endless flexible cutting chain ( 108 ). A guard ( 162 ) is moved relative to the chain ( 108 ) by means of pivoting of the handles ( 114, 116 ) relative to each other to grip vegetation between the guard ( 162 ) and the chain ( 108 ). A gear mechanism is connected between the guard ( 162 ) and the chain ( 108 ) such that pivoting of the handles ( 114, 116 ) through a first angle relative to each other causes pivoting of the guard and chain through a second angle, larger than the first angle, relative to each other.

The present invention relates to a vegetation pruning device and hasparticular, although not exclusive, relevance to such a device as wouldbe used for gardening purposes.

There are a considerable array of tools available for the moderngardener in order to be able to keep growth of vegetation under control.The term “gardener” is meant not only to encompass small domesticconcerns, but also larger more agricultural endeavours. Whatever thenature of the gardening, however, there will be a need to control therate of growth of vegetation for either aesthetic or other purposes suchas crop yields etc.

Among the many tools available for keeping vegetation growth undercontrol are, for example, shears for pruning or cutting “light”vegetation such as grass or leaves or small twigs etc. Shears operate bypivoting a pair of blades located in parallel planes relative to eachother so that shear forces are applied to vegetation placed in the anglebetween the blades, the cutting force being generated by manual force ofthe user, applied to handles attached to the blades. The size orthickness of vegetation which can be cut by shears is limited to theamount of manual force which can reasonably be applied to the handles bythe average user. Known shears also suffer from the disadvantage thatthe act of pivoting the arms of the shears relative to each other toeffect cutting tends to push vegetation being cut away from the gapbetween the blades of the shears, which makes the it more difficult toeffect cutting of the vegetation.

At the other end of the scale there are hedge trimmers and the so-calledchain saw used for “heavy” vegetation cutting such as trees (whethersmaller branches or the entire tree).

Additionally there are smaller-scale tools such as secateurs or scissorsused for more delicate pruning or cutting operations.

In any event it will be appreciated that the modern gardener will moreusually choose a tool specific to the particular type of pruningoperation required. For example, and with reference to the above, whenlight pruning is necessary of, for example, domestic flowers, then thesecateurs are likely to be chosen. Alternatively if bushes are to bepruned, or grass is to be cut, then shears will often be chosen.

There exists, however, a gap in the tool array when moving from “light”bushes to “heavy” trees. Very often vegetation will be of such a sizeand nature (such as larger bushes or small trees) which are either of adensity or branch diameter too large for shears or hedge trimmers tocope with but for which use of the chain saw is unnecessarily excessive.

It is, therefore, an object of the present invention to provide avegetation pruning device which at least alleviates the aboveshortcomings by providing a novel form of tool which fits nicely in thisgap. Provision of such a tool provides a compact and safe arrangementwhereby pruning of the “heavier” vegetation is possible without the needto resort to the aggressive and particularly dangerous tool such as achain saw.

A known type of chain saw is disclosed in U.S. Pat. No. 4,294,012 andhas a guard pivotable relative to a blade of the chain saw and locatedin a plane parallel to the plane of the chain saw blade, to enable theguard to either be inserted beneath a log to be sawn, to reduce thetendency of the sawn piece of log to pinch the chain saw blade, or tograsp small branches to be sawn and force them into the chain saw. Thechain saw has a first handle arranged on the chain saw body, and asecond handle connected to the guard, so that the guard can be pivotedrelative to the chain saw blade by pivoting the handles relative to eachother.

However, this arrangement suffers from the drawback that for a givenforce manually applied by the user to urge the handles together, theclamping force grasping vegetation between the guard and the chain sawblade can become excessive. This in turn results in excessive electriccurrent being drawn by the chain saw motor to enable the chain saw tocut, as well as causing excessive wear to the cutting chain and chainsaw guard.

Preferred embodiments of the present invention seek to overcome theabove disadvantages of the prior art.

According to the present invention, there is provided a vegetationpruning device comprising:

-   -   a pair of arms adapted to pivot relative to each other about an        axis to adjust the angle between said arms, wherein each said        arm has at least one respective handle portion adapted to be        gripped by a user;    -   a motor having a rotary output drive;    -   an endless flexible cutting element mounted to a support and        adapted to be driven relative to said support by means of said        rotary output drive to cut vegetation presented thereto;    -   at least one gripping member adapted to be moved relative to        said cutting element by means of pivoting of said arms relative        to each other to grip vegetation between said gripping member        and said cutting element; and    -   a gear mechanism connected between at least one said gripping        member and at least one said arm, wherein pivoting of said arms        through a first angle relative to each other causes pivoting of        said gripping member and said support through a second angle,        larger than said first angle, relative to each other.

By providing a gear mechanism connected between at least one saidgripping member and at least one said arm, wherein pivoting of said armsthrough a first angle relative to each other causes pivoting of saidgripping member and said support through a second angle, larger thansaid first angle, relative to each other, this provides the advantage ofreducing the gripping force between the gripping member and the cuttingelement for a given force applied between the arms, which results inless electric current being drawn by the motor. This in turn providesthe advantage of enabling a motor of lower power (and therefore lessweight) to be used, as well as reducing wear on the gripping member andcutting element, and enables a user to reach further by means of thetool, since the user's hands can be closer together.

The gear mechanism may comprise at least one first gear element mountedto a said arm and at least one second gear element mounted to a saidgripping member and engaging a said first gear element.

At least one first gear element and/or at least one said second gearelement may comprise a respective segment of a respective gear wheelcorresponding to pivoting movement of said arms through less than 180degrees.

By only providing segments of gear wheels corresponding to the requiredrange of angular movement of the arms relative to each other, thisprovides the advantage of enabling the device to be constructed morecompactly and/or of less weight.

At least one said gripping member may be provided with at least oneprotrusion for resisting rotation of vegetation gripped between saidgripping member and said cutting element relative to said grippingmember.

This provides the advantage of further assisting the cutting operation.

At least one said gripping member may have at least one respectivecurved edge facing towards said cutting element.

At least one said protrusion may be defined by a respective notch in asaid curved edge.

At least one said gripping member may be pivotably mounted relative toone of said arms.

The motor may be mounted to a first said arm.

The pruning device may further comprise at least one power supply forpowering said motor, wherein at least one said power supply is mountedto said first arm on a side therefore opposite to said motor.

By mounting at least one power supply on said first arm on a sidethereof opposite to said motor, this provides the advantage ofdistributing the weight of the pruning device as evenly as possible.

Preferably, the arms are pivotable between a first position allowingaccess to said cutting element, and a second position in which thecutting element is substantially inaccessible.

This feature enhances the safety of the device when the sheararrangement is in its closed position. It prevents the user accidentallyputting their fingers or hands in contact with the cuttingelement—something which is desirable to avoid.

The pruning device may further comprise first biasing means for biasingsaid arms towards said second position.

At least one said gripping member may be provided on a first said armand the device may further comprise a guard member provided on a secondsaid arm.

The guard member may be moveable between a first position allowingaccess to said cutting element and a second position preventing accessto said cutting element.

This enables access to the cutting element, for example to replace itwhen it becomes worn.

The pruning device may further comprise second biasing means for biasingsaid guard member towards said second position.

The guard member may be moveable to said first position only when saidarms are in said second position.

At least one said gripping member and/or said guard member may beresiliently biased towards the cutting element and movable awaytherefrom under application of force.

This again is a safety feature which obviates the need for the user fromcontacting the cutting element or vegetation in the region of thecutting element but still permits the cutting element, having but thevegetation, to pass therethrough.

At least one said gripping member and/or said guard member may comprisefirst vegetation restraining means having a series of indentations andor projections disposed towards said cutting element to provide pointsof restraint or retention of said vegetation thereagainst.

This allows for the vegetation to be cut to be held in abutment with thecutting element by use of the shears themselves and thus reducing thepotential for injury of a user's hand or fingers coming into contactwith the cutting element. Since the cutting element is powered therewill often be associated therewith considerable movement of the cuttingelement which will otherwise tend to dislodge and move the vegetationbeing cut and thus it is desirable to restrain such motion against thecutting force applied by the cutting element.

At least one said gripping member and/or said guard member may beassociated with said cutting element so as to be displaceable away fromsaid cutting element by said vegetation through which said cuttingelement has cut.

At least one said gripping member and said second member may be adaptedto engage each other at least adjacent respective ends thereof remotefrom said axis when said arms are in said second position.

The pruning device may further comprise a further guard member forpreventing access to said cutting element at an end thereof remote fromsaid axis.

The further guard member may be adapted to lock a said gripping memberand said guard member together when said arms are in said secondposition.

The pruning device may further comprise first locking means forreleasably locking said arms in said second position.

A second said arm may comprise second vegetation restraining means forrestraining vegetation inserted between said pair of arms fromdisplacement when engaged with said cutting element.

The second vegetation restraining means may comprise a series ofindentations and or projections disposed towards said cutting element toprovide points of restraint or retention of said vegetationthereagainst.

The series of projections may comprise a plurality of teeth inclined andfacing towards said cutting element.

The second arm may comprise a substantially parallel pair of side wallsdefining a channel therebetween for at least partially receiving saidcutting element as the cutting element is pivotally displaced towardssaid second arm.

The pruning device may further comprise at least one stop member tolimit pivotal displacement of said arms towards one another forrestraining said cutting element at a predetermined pivotal positionrelative to said second arm so as to remain received within saidchannel.

This specifically allows the other of said arm to restrain thevegetation as it brought into engagement with the cutting element butsince such vegetation being cut will lay transversely across these twoarm members then as the cutting element passes into the channel it willeffect complete cutting of any vegetation supported on theses pair ofsidewalls.

The channel may comprise an inner surface extending between saidsubstantially parallel side walls defining a dust/debris conveying pathcommunicating with a dust/debris extraction aperture.

The substantially parallel pair of side walls may be profiled to allowat least part of said cutting element to pass completely through saidchannel as said cutting element is pivotally displaced towards saidother of said pair of arms.

The side walls may have a V-shaped profile for receiving and supportingin an inner apex thereof vegetation to be cut.

The specific use of a V-shaped profile permits accurate holding ofvegetation of different diameters at a predetermined, usually central,position relative to the cutting element.

The motor rotary output drive may include a toothed drive wheel.

The motor may have an output gear adapted to rotate about an axissubstantially parallel or substantially perpendicular to the axis ofrotation of said rotary output drive.

The cutting element may be mounted upon a support member and arrangedfor rotation thereabout under the influence of the rotary output drive.

The support member may include a driven and a drive wheel around whichthe cutting element moves as the drive wheel rotates.

The cutting element may rotate within a first plane and the arms of thepair of arms each include a surface which extends either side of thisfirst plane.

The cutting element may comprise a chain.

The teeth of the toothed wheel may fit between the links of the chain inuse to provide motive force to the chain.

The chain may further include a plurality of barbs to assist invegetation pruning.

The pruning device may further comprise an actuator for controllingoperation of the motor.

The actuator may be a variable speed-controller for governing the outputspeed of the motor.

The actuator may comprise at least one resiliently biased switch membermounted on each of the two arm members, wherein said actuator isrestrained from operating said motor unless at least one said switchmember on each arm is operated.

This ensures that the pruning device can only be operated when the useris grasping both arm members and thus using the tool correctly. In theevent that the user has an accident resulting in loss of grip on one orother of the arm members the at least one switch member mounted thereonwill no longer be operated causing the motor to be stopped and thuspresenting an additional safety feature. Such resiliently biased switchmember may provide either mechanical or electrical restraint of theactuator when in a non-operated position.

The pruning device may comprise a self adjusting tensioning device toallow automatic adjustment of the support member.

Adjustment of said support member may effect tensioning of said cuttingelement.

The self adjusting tensioning device may comprise adjustable restraintmeans for releasably securing said support member relative to saidpruning device together with a rigid support block rigidly secured toone of said pair of pivotally coupled arms on which said support memberis mounted, said block having a resiliently biased adjustment memberdisposed between said support block and said support member to exert adisplacement force on said support member away from said support blockwhen said restraint member is in a released position.

The biasing member may comprise a spring biased plunger having a firstratchet member and said support block having a second ratchet memberwhereby engagement between said first and second ratchet membersprevents displacement of said plunger towards said support block.

The pruning device may further comprise a lubricating device fordepositing lubricating material on said cutting element.

The lubricating device may include a reservoir for lubricating materiallocated within a second said arm.

The lubricating device may be adapted to deposit a predetermined amountof lubricating material on said cutting element in response to openingof said arms relative to each other and/or opening and closing of saidarms relative to each other.

The motor may be an electric motor adapted to be switched so as toeffect braking of said cutting element.

Several preferred embodiments of the present invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings of which:

FIG. 1 shows a side view of an embodiment of the invention with the jawsof a pair of jaws in the “closed” position;

FIG. 1 a is a schematic inverted view of the jaws of the embodiment ofFIG. 1 showing in ghosting the internal working mechanism thereof;

FIG. 1 b is a cross sectional view of one of the jaws of the embodimentof FIG. 1 a along the lines I-I;

FIG. 1 c is an opposed side view of the embodiment of FIG. 1;

FIG. 2 shows the side view of FIG. 1 but with the jaws of the pair ofjaws in the “open” position;

FIG. 3 is a front perspective view of the embodiment of FIG. 1 with thejaws in an open position;

FIG. 4 shows a side view of the embodiment of FIG. 1 with arepresentative vegetation sample having been partially cut;

FIG. 5 shows the continued cutting of the vegetation from FIG. 4 but ata more advanced stage;

FIG. 6 illustrates schematically the internal mechanism of the apparatusof FIG. 2 taken along the sectional line X-X;

FIG. 7 shows a sectional view through part of the chain cutting element;

FIG. 8 is an enlarged cross sectional view of an alternative embodimentof the present invention illustrating an improved self adjusting bladetensioning device;

FIG. 9 is a perspective view from one side of the self adjusting bladetensioning device of FIG. 8;

FIG. 10 is a front view of the self adjusting blade tensioning device ofFIG. 9;

FIG. 11 is a perspective view of a further embodiment of the presentinvention with the jaws thereof in a substantially closed position andwith the chain bar and cutting chain thereof removed;

FIG. 12 is a detailed view of the jaws of the embodiment of FIG. 11 inan open condition with the chain bar and cutting chain present;

FIG. 13 is a perspective view of two cooperating parts of a housing ofthe embodiment of FIG. 11 in a disassembled condition; and

FIG. 14 is a perspective view of one part of the housing and gearmechanism shown in FIG. 13.

Referring particularly to FIG. 1 of the drawings, a vegetation pruningdevice shown generally as 2 is shown. In the example shown in FIG. 1, itcan be seen that the pruning device comprises a pair of pivotallycoupled arms 4 and 6. In this example the upper arm 6 of the pair ofarms 4, 6 comprises a composite structure formed from a cutting element8 and an outer portion 10 biased towards the cutting element 8. A pivotpoint 12, in this embodiment an appropriate through bolt, articulatesthe first arm 4 of the pair of arms to the second arm 6 of the pair ofarms so that the arms 4, 6 can be “open” and “closed” by appropriaterelative movement of respective handles 14 and 16 of the arms. Thehandles 14, 16 are arranged in a plane generally perpendicular to theaxis passing through pivot point 12 about which arms 4, 6 pivot relativeto each other.

Referring now particularly to FIG. 2 it can be seen that a user may movethe handles 14, 16 apart from one another (as indicated by arrow A) suchthat the arms 4, 6 also move apart from one another to the “open”position via the pivot point 12. It can be seen from this figure thatopening the arms 4, 6 exposes the cutting element 8 such that vegetationfor pruning may be introduced into the space between the arm 4 andcutting element 8. The corollary to this, of course, is that in FIG. 1,where the arms 4, 6 are shown in the “closed” position, the cuttingelement 8 is generally shielded such that it is substantiallyinaccessible. This will become more understandable from the descriptionbelow and particularly with reference to FIG. 6.

Referring now particularly to FIG. 3 it can be seen that the cuttingelement 8, in this example a linked chain, passes over a support member,in this example a longitudinally extending chain bar 20. A longitudinalsection taken through the chain 8 is shown in FIG. 7. It can be seenhere that the chain 8 comprises a plurality of links 22 which serve tointerconnect sets of pairs of chain elements 24. The construction of thelinked chain 8, in this manner, therefore, is conventional. Such a styleof chain is used, for example, in chain saws for cutting trees and alsoon bicycles and motorbikes for providing motive force. Also shown inFIG. 3, although not essential to the operation of the invention, are aplurality of barbs 26 coupled to the chain 8 used to assist in thecutting operation of the chain 8. It will be apparent to those skilledin the art that a conventional chain saw uses a linked chain with suchbarbs attached thereto. The purpose of the barbs 26 is to provide thecutting or slicing action of the chain in the vegetation to which it ispresented. This chain 8 and chain bar 8 are similar to those employed ina conventional chain saw but, for the purpose of understanding thepresent invention, simply represent a powered cutting element.

It can also be seen from FIG. 3 that the chain 8, which is mounted uponand surrounds the chain bar 20, extends within a plane shown as ABCD inthe drawing. It can be seen from FIG. 3 and also FIG. 6 that the arm 4,and the outer portion 10 of arm 6 includes side coverportions-respectively 4 a, 6 a and 4 b, 6 b-which serve, when the arms4, 6 are in the “closed” position (in FIG. 1), to at least partiallyencapsulate or surround the chain 8. With reference to FIG. 1 a it isseen that the cover portion 6 comprises two substantially parallel sideplate members (6 a and 6 b) having a space therebetween slightly greaterthan the maximum width of the chain and/or chain bar 20. The outermostedges 6 c of each of the plates 6 a and 6 b are interconnected by asubstantially perpendicular outer plate member (not shown) such thatthis arm portion 6, in cross section, presents a substantially U-shapedprofile into which the chain (or powered cutting element) may be atleast partially accommodated. The front end of this arm 6 is furthercurved so as to partially enclose the front end of the curved end of thecutting element as shown in FIG. 1 a. It is also possible for the arms4, 6 to abut each other at their front ends in the closed position tocompletely restrict access to the front end of the cutting element8.This significantly improves the safety of the apparatus, sinceaccidents can result from inadvertent contact between the front end ofthe cutting element 8 with a workpiece or the ground, causing loss ofcontrol over the apparatus, or the flex supplying electric power tomotor 36 can be inadvertently cut by passing into the gap between thearms 4, 6.

Alternatively, or in addition, a so-called nose guard (not shown) can beprovided which restricts access to the front end of the cutting element8. This can abut or enclose the front ends of arms 4, 6 when in theirclosed position to also prevent opening of the arms 4, 6 relative toeach other.

With regard to FIGS. 1 a and 1 b the proposed arm member 4 is againprovided with a substantially U-shaped cross sectional profile (FIG. 1b) into which at least part of the chain 8 may be accommodated (asindicated in hashed lines in FIG. 1 b). Thus in the enclosedconfiguration, the arm members 4 and 6 serve to at least partiallyencompass the powered cutting element (chain 8). Both arms 4 and 6 areprovided with curved front end portions to also partially enclose thefront curved end of the cutting element.

It can be seen from FIG. 1, therefore, that when the arms 4, 6 are in aclosed position direct access to the chain 8 (and, in particular thebarbs 26 attached thereto) is not possible. This provides a significantsafety feature for the user of the vegetation pruning device 2 inaccordance with the present invention. By providing that each of thecover portions 4 a, 4 b and 6 a, 6 b of their respective arms 4, 6extend in a direction parallel with the plane ABCD, yet each of theseextensions are arranged to be laterally offset both from the plane inwhich the chain 8 rotates and physically from the chain 8 itself, thenaccess to the chain 8 by user from a direction perpendicular to thisplane ABCD is not possible when the arms 4, 6 are in a closed position.The arm members 14 and 16 are designed so that when brought into theclosed configuration as shown in FIG. 1 the handle portions will engageone another to define a limited end stop to the pivoted closed position(FIG. 1). In this embodiment, the arm member 16 is provided with a motorhousing 17 (to be described below) against which an inner portion 19 ofthe upper handle 14 (the term inner used to indicate proximate pivotaxis 12) which engages to define this end stop position (FIG. 1). Thisdefined end stop position causes the side cover portions 4 a and 4 b ofthe arm 4 to partially enclose the blade but retain the arm portion 4 ina position whereby its inner face 4 c (FIG. 1 b) is restrained fromengaging with the blade 8 as shown. Thus, the arm member 4 whilst ableto partially enclose the cutting element is restrained from engagementtherewith when in an enclosed configuration. Similarly, and as will bedescribed in more detail below, the upper arm 6 is pivotally biased tothe position substantially shown in FIGS. 1, 1 a and 2 so that it willpartially enclose the cutting element or chain 8 but has a stop positionas shown which prevents it from being displaced into engagement withsuch cutting element, again allowing the cutting element to be partiallyenclosed thereby but is restrained from interference with such cuttingelement operation.

It can be seen from the figures that, in this embodiment, the arm 4 hasa plurality of indentations or projections thereon, in this exampleprojecting teeth 28, which are employed in use of the pruning device, torestrain vegetation being cut by the chain 8 in a largely immovableposition relative to the arms 4, 6 and the cutting element 8. It will beapparent that in order to effect efficient pruning of vegetation, thevegetation to be pruned needs to be held steady relative to the cuttingelement so that an accurate cut can be obtained. The purpose of theteeth 28, therefore, is to achieve such function. If desired, the teeth28 could also be formed on the arms 6 in addition or alternatively tothat of the arm 4. Also any suitable shape or profile of suchindentations or projections which achieve the holding the vegetationsteady relative to the cutting element are equally efficacious. As seenin FIGS. 1 and 2 the direction of rotation of the chain 8 is indicatedby the arrows on the chain bar 20. The specific use of the saw toothteeth 28 is such that rotation of chain 8 will cause it to engage withany workpiece placed between it and the jaws 4 whereby the cuttingaction will attempt to displace the branch or workpiece in a directiontowards the pivot axis 12 which will, in practice, serve to drive suchworkpiece or branch into positive engagement with the teeth 28 thereforeenhancing the gripping effect resultant from use of such teeth 28. Ifteeth are employed on the arm member 6 then it is preferred such sawteeth will be inclined in an opposite direction to that of arm 4 so asto again cause any workpiece being cut to be forced into positiveretaining engagement therewith in a similar manner to employment of theteeth 28.

In order to provide a motive drive force to the chain 8 the proximal end(that is the one remote from the plane ABCD in FIG. 3) of the chain bar20 includes a drive wheel or sprocket 30 (shown in FIG. 1 a and FIG. 6but not visible in the other figures) which engages and drives the chain8 in a conventional manner.

Also, it will be apparent, that the distal end of the chain bar 20includes a driven wheel or sprocket 32 (again, shown in FIG. 1 a andFIG. 6 but not visible in the other figures) to allow rotation of thechain 8 around the chain bar 20. The chain 8, when driven by the drivesprocket 30, therefore, rotates in a continuous loop about the externalperiphery of the chain bar 20. It can be seen from FIG. 6 that the drivesprocket 30 is coupled to an output shaft 34 of an electric motor 36. Inthe example shown the motor 36 provides a direct rotary output for theoutput shaft 34, although those skilled in the art will appreciate that,dependent upon the conditions of use of the pruning device, a gearbox(not shown) between the motor 36 and the drive sprocket 30 may be usefulin order to adjust the amount of torque and/or the rotational speedexhibited by the chain 8 as it is being driven. In this manner, thecutting element operates as a conventional cutting element of a chainsaw.

Power for the motor 36 is provided in conventional manner by powersupply cable 38 which will be coupled to a source of mains power or thelike. (Alternatively, albeit not shown, power could be supplied by abattery or petrol engine). In one particularly advantageousimplementation of the invention, the motor 36 is powered by arechargeable battery, which is arranged on the housing of the apparatuson the opposite side to the motor 36. This allows a particularlyergonomic arrangement in which the weight of the rechargeable batterybalances that of the motor 36 so that the centre of gravity of theapparatus is as near as possible to the central plane of the apparatus.Operation of the motor 36 is dependent upon actuation of a triggerswitch 40 by the user of the device 2. The trigger switch 40 isconveniently mounted upon one of the handles, in this example, handle14. By mounting the trigger 40 on the handle it is easy for the user ofthe device not only to hold and operate the device, but then also tohave a readily available means of activating or deactivating the motor36. Additionally, it is entirely feasible (although optional) for thereto be a secondary operating device mounted upon the other handle 16.This would operate as a “failsafe” mechanism whereby unless bothactuators were depressed or activated by the user then the device wouldbe inoperable. This is useful in situations such as those where the userwould be in an elevated position up a ladder, or the like, and possiblyreaching in order to cut vegetation. It is known that these situationsare potentially dangerous and so ensuring that the user must have bothhands on the pruning device 2 in order to operate it is desirable. Anexample of such a secondary failsafe mechanism is illustrated by asecondary displaceable switch member 41 which again is readilyaccessible via a users fingers when gripping the handle 16. The use ofdual switching mechanisms are conventional within many forms of powertools and their specific operation need not be described in any greatdetail here. However, their operation may be electrical or a combinationof electrical mechanical mechanisms. For example operation of the motorwill be prevented unless both switch elements 41 are displaced from anunactuated to an actuated position. In this manner the failsafemechanism may simply comprise an electrical connection to the motorrequiring a dual electrical input or may in fact provide some form ofmechanical stop mechanism preventing electrical connection between theswitch member 41 and the motor. A particular advantage in this inventionwill be determined that should the users grip on either handle bereleased then operation of the motor is immediately stopped.

The trigger switch 40 in this embodiment not only controls actuation ofthe motor 36 but, dependent upon the amount of pressure applied theretoby user, dictates the speed of output of the motor 36. Such switches arereadily available in the art.

The safety of the pruning device can be further enhanced by having abraking arrangement for bringing the chain 8 to a halt as quickly aspossible when power to the motor 36 is interrupted. One way of achievingthis is to arrange for the motor 36 to be short circuited when theswitch 40 is released, so that the motor 36 acts as an electromagneticbrake.

It will be appreciated from the above that the teeth of both the drivesprocket 30 and the driven sprocket 32 operate to engage the chain 8 ina conventional manner. Clearly the frictional contact which occurs byvirtue of this engagement and also the wear of the chain 8 around theperiphery of the chain bar 20 may cause a significant amount of heat tobe generated. It is therefore advisable for not only some lubrication tobe applied to the entire cutting element mechanism including its drivemeans, but also a mechanism provided for varying the tension felt by thechain 8 if it wears during use.

In order to provide lubrication for the chain 8 and its drive mechanism30, 32, 34 therefore, there is provided an oil reservoir 42 mountedadjacent the drive sprocket 30 and able to dribble lubricating oil ontothe drive sprocket 30 during use of the motor 36. The lubricationmechanism can have a lubrication reservoir (not shown) arranged insidethe lighter handle 14, as a result of which the apparatus is of compactconstruction, and the weight of the apparatus is balanced as evenly aspossible. The lubricating mechanism can be arranged to dispense a fixedamount of lubricant in response to opening of the handles 14, 16relative to each other, or in response to opening and then closing ofthe handles 14, 16 relative to each other. It is also possible for thelubricating mechanism to take higher levels of heating of the chain 8into account by controlling the amount of lubricant dispensed independence upon the speed at which motor 36 is driven, so that morelubricant is dispensed at higher operating speeds of the motor 36.

The chain tensioning mechanism employed in this specific embodiment isagain one conventionally employed in the art of chain saws. The chainbar 20 (as is shown in FIG. 1 a) is securely mounted to the arm member16 in the region of the motor housing 17 by an appropriate threaded boltmember (not shown). Such a threaded bolt member will have a firstengaging face against which one side of the chain bar 20 is received anda second threaded nut member is then rotatably received on such bolt soas to compress the chain bar 20 therebetween. Operation of this nut orbolt can be achieved in a number of conventional manners but willusually employ an external sprocket member which can be manually rotatedas appropriate. In the event that use of the cutting element causes aloosening of the chain (such as by stretching of the distance betweenadjacent link elements), the chain bar 20 may then slideably displacedabout this bolt member in a direction away from the pivot axis (12) ofthe pruning device by firstly loosening the nut member of the nut andbolt restraining mechanism and manually displacing the blade in adirection away from such pivot axis 12 effectively increasing thedistance between the sprocket 32 and the sprocket 30 causing thetightening of the chain thereabout. Once appropriate tightening has beenachieved the chain bar 20 is fixed into the new position by appropriateretightening of the nut and bolt member. This chain tension device isconventional for chain saws.

Referring now to FIGS. 4 and 5, in that order, operation of the device 2will be described. The large cylindrical object 44 in the drawings isrepresentative of vegetation to be pruned and, in this example, is meantto represent a section of a branch or a bush or the like. Assumingfirstly that the arms 4, 6 are in the “open” position (FIG. 2) and thebranch 44 is placed between the lower surface of the chain 8 adjacentthe teeth 28 of arm 4, then the user will close the handles 14, 16 ofthe device until such time as the branch 44 contacts the lower surfaceof the chain 8 with its upper portion 44 a and the teeth 28 of the arm 4with its lower portion 44 b. As the user squeezes the trigger 40, thechain 8 is caused to rotate and the barbs 26 formed thereon will cutinto and through the branch 44 in known manner. Whilst this isoccurring, the user continues to effect closing of the handles 14, 16 soas to effect a biasing force on the branch 44 into engagement with suchcuffing element. As the handles 14, 16 move closer together, the forceapplied thereto acting through the pivot point 12 causes the arms 4 and6 also to move closer together. In this manner, therefore, the branch 44is effectively squeezed between the lower arm 4 and the chain 8 and itschain bar 20 causing cutting of the branch 44. The position in FIG. 4,therefore, is that of the branch 44 having been cut through about halfof its diameter.

Because the handles 14, 16 are located in a plane generallyperpendicular to the pivot axis passing through pivot point 12, thesqueezing action of the user pushing handles 14, 16 towards each otherminimises the extent to which substantial sidewards torque is applied tothe pruning device as a result of this action. This in turn enables theuser to maintain better control of the pruning device.

Continued force applied to the handles 14, 16 in order to bring themcloser together results in the position shown in FIG. 5. Here it can beseen that the arm 4 has been brought into its completely closed positionsuch that the side cover portions 4 a and 4 b of the arm member 4effectively shield the lower portion of the chain 8 from any contact bythe user although the teeth 28 still engage in retaining the brancheither side of such cutting element (as shown). It will be noticed,though, that the outer portion 10 of the upper arm 6 has been pivotallydisplaced from its position as shown in any of the other figures. Inthis particular embodiment, the upper portion 10 of the upper arm 6 ispivotally connected to such arm members 6 and biased towards an end stopposition as shown in FIGS. 1 and 2 so as to closely abut and partiallyenclose the cutting element or chain 8. This functions as a chain guardmechanism. However, such a chain guard, if not pivotal, would limit thedepth of branches that could be cut to the depth of the chain bar 20.However, by making such outer portion 10 pivotal, then as the branch 44passes over the chain bar 20 during the cutting operation and as shownin FIG. 5, the upper portion 44 a will eventually be forced in abutmentwith this outer portion 10 whereby the continued displacement of thebranch past the cutting bar will effect pivotal displacement of theouter portion 10 as shown in FIG. 5 allowing the branch to continue tomove past the chain 8 and the chain bar 20 in order to effect completecutting thereof of any branch having a depth greater than that of thechain bar 20. Once the cut branches are then removed from the pruningdevice, the spring biasing of this outer portion 10 causes this portion10 to move back into position shown in FIG. 1 effectively providing itsfunction as a chain guard. As mentioned, this chain guard is limited inits pivotal displacement so as not to be brought into engagement withthe chain but to partially encompass it as shown in FIG. 1 a. Thisprovides for a variable cutting depth irrespective of the depth of thechain bar 20.

Having a movable portion of the arm 6 is necessary in this example asthe portions 6 a, 6 b of the arms which sit either side of the chain 8in the direction perpendicular to the plane ABCD would otherwise simplyabut the upper surface of the branch 44 and prevent further closing ofthe arm 4 toward the chain 8 and chain bar 20. As shown in from FIG. 5,the spring providing the spring loading of outer portion 10 of the arm 6is shown at 46.

Referring now to FIG. 1 c, showing the opposed side of the pruningdevice of FIG. 1, the device is provided with an appropriate dust orchip extraction aperture 100. As will be appreciated from FIGS. 4 and 5,the cutting operation of the chain 8 causes wood chippings and sawdustto be drawn towards the motor housing 17 and sprocket 30. Such movementis further enhanced by the formation of the U-shaped channel formed inarm member 4. As such, a lower portion of the motor housing 17 isprovided with an appropriate internal channel and external aperture 100so that any sawdust or wood chippings drawn into the motor housing aresimply extracted so as to fall out of this aperture whereby the speed ofrotation of the chain will create an appropriate airflow serving todrive the wood chippings out of the tool.

One of the major benefits of the current invention is the ability toprovide a means of rigidly securing the branch or workpiece 44 in closeproximity with the blade during the cutting operation. In thisparticular embodiment a further enhancement provides that the cuttingelement is partially encompassed so as to prevent inadvertent accessthereto providing an enhanced safety feature for the operator. In afurther variant (not shown) the invention can be further modified sothat operation of the cutting element of the embodiment in FIGS. 1 to 5is prevented in the absence of an article to be cut being placed betweenthe cutting element and the jaw 4. This could be achieved by providingan appropriate sensing mechanism registering the presence of a branchbetween such cutting element 8. An example would be the provision of afurther limited pivot action of the lower arm 4 which would be biased tothe position conventionally shown in FIGS. 1 to 5. The degree of pivotaldisplacement of this arm 4 about this additional pivot point would belimited to only a few degrees whereby when a branch is displaced betweenthis arm 4 and the cutting element 8 and the jaws closed, the resistanceof the branch 44 would cause a slight pivotal displacement of the arm 4against its associated biasing. Detection of this pivotal displacementwould then be indicative of the presence of a branch to be cut and anappropriate facility employed within the device to allow operation ofthe motor on activation of the switches as previously described. Again,such feature could be mechanical or electrical. In the event of anelectrical operation, one example would be that when the jaw 4 is in itspivotally closed position as shown in FIGS. 1 to 3, then an appropriateelectrical contact activates an appropriate switching element preventingoperation of the motor. Once such electrical contact is broken (by thepivotal displacement effected by detection of a branch) operation of themotor can then be initiated. A further enhancement of this type ofpivotal detection system will be that once the branch has beencompletely cut through and falls away from the tool such biasing forceon the jaw 4 will be removed causing it to return to its normal positionby the inherent resilient biasing causing closure of the aforementionedelectrical contact and hence cessation of operation of the motor,stopping the tool. Thus, not only would this permit the tool to beoperated only in the presence of a branch but that operation of the toolwould automatically cease once that branch had been completely cutthrough.

Although in the example shown in FIGS. 1 to 5 the cutting element 8 andthe outer portion 10 of the arm 6 biased towards the cutting element 8together comprise one arm 6 of the pair of arms 4, 6, it will beappreciated that these may be formed as separate elements. For example,it could equally be the case that whilst one arm 4 of the pair of armsis a shown in the drawings, the other arm could actually comprise thechain bar 20 and its associated chain 8. In this example, therefore, thefeature which is labelled 10 in the diagrams would not actually formedpart of the other arm of the pair but would be a pivoting spring biasedportion formed as a separate element. This distinction is not germane tothe present invention, however.

It will be understood by those skilled in the art that the sense ofrotation of the chain 8 about its chain bar 20 determines theorientation of the teeth 28. Also this sense of rotation will determinebetween which arm 4 or 6 as shown in the drawings and the chain 8 thebranch 44 to be cut is presented. Clearly it is not useful for the chainto rotate in the sense which causes the branch 44 to be pushed away fromthe pruning device but rather pulled in towards the pruning device 2and, even then, to be engaged in as non-movable a manner as possible bythe teeth 28.

In a further enhancement of the present invention, now shown in FIGS. 8through 10, there is provided a self-adjusting blade or chain tensioningdevice to replace the manually adjustable chain tensioning device shownwith reference to FIG. 1 a.

Referring now to FIG. 8 there is a shown an alternative pruning device2″(identical to pruning device 2 of FIG. 1 with the exception of thischain tensioning device) having such a modified blade tensioning deviceshown generally by arrows 450. As discussed above, where the cuttingelement comprises a chain 458 mounted on an appropriate support member(or chain bar) 460 for such chain 458 to extend between a first drivenwheel or sprocket member 462 and a driven (or sprocket) wheel member 464then use of the cutting chain 458 will incur considerable vibration,often effecting displacement of the support member 460 thus causing thechain to loosen. It is necessary that the support member 460 isadjustable so as to allow the chain to be retensioned as appropriate.

Referring now to FIG. 9 the self-adjusting device 450 is shown in moredetail.

This device 450 comprises a primary mounting block 466 securely mountedto the motor housing 417 and hence handle portion 416 so as to beeffectively integral therewith. Adjustably mounted on this mountingblock 466 is a steel compression plate 468 which is adjustable relativeto and away from the mounting member 466 (as indicated by arrow 500) soas to effectively compress or release an internal end portion 470 of thesupport member 460, as schematically illustrated in FIG. 8. Here it canbe seen that the inner portion 470 of the support member 460 has asubstantially rectangular rebate 461 allowing it to pass over anappropriate screw threaded member (not shown) upon which the compressionplate 468 is mounted whereby a conventional wing nut (471) or otherrotatable member (eg. a rotatable knob) can then be used to adjust thecompression plate towards or away from the mounting member 466 so as tocompress and hold, or alternatively, release the support member 460disposed between such plate 468 and block 466. Accordingly, thiscompression plate 468 is a greater size than rebate 461 to allowpositive engagement of the plate 468 with the support member 460. Thedevice 450 is further provided with an internal elongate channel 472slideably accommodating a plunger 474 which is spring loaded via anappropriate coil spring 476 disposed between an internal end of thechannel 472 and the plunger 474 as shown. The channel 472 issubstantially square in cross section so as to retain the plunger in adesired displaceable orientation relative to the support member 460 aswill be described below. The plunger is further provided with a seriesof ratchet teeth 476 inclined in a direction away from the mountingblock 466 as shown. An appropriate non-return ratchet pawl 478 is thenrigidly connect to the mounting member 466 so as to engage with theratchet teeth 476 to prevent a return of the ratchet member 476 backinto the mounting member 466 once displaced there out of by the springmember 476. In practice, this non-return ratchet pawl will be providedwith an appropriate adjustment means which allows it to be displaced outof engagement with the ratchet teeth when the self-adjusting device isto be released to allow removal of the chain and necessary reduction intension thereof to allow such removal.

In practice, the support member 460 and the self-adjusting device 450will be constructed as shown in FIG. 8 with an outer end surface 480 ofthe plunger 474 in abutment with an internal surface 482 of the rebate461 of the support member 460 as shown in FIG. 8. When the compressionplate 468 is in a released position, disposed away from the block 466,the support member 460 is no longer frictionally restrained against themounting block 466, whereby the inherent resilient biasing of the coilspring 476 (which is set at between 5 lbs and 10 lbs pressure in anormal embodiment but could be anywhere between 5 lb and 30 lbs ofpressure) exerts a biasing force on the plunger 480 which is exertedagainst the internal surface 482 of rebate 461 so as to effectadjustment of the support member away from the support blocking adirection as shown by arrow 490 in FIG. 8. The amount of displacementeffected on the support member 460 by such biasing force is limited bythe size of the chain member 458 but in this released configuration theself-adjusting device 450 serves to apply sufficient force to thesupport member 460 to effect appropriate tensioning to the chain 458 asrequired. The compression plate 468 can then be adjusted so as to clampthe support member 460 against the mounting member 466 to hold it in theself-adjusted, tensioned configuration. In practice the non-returnratchet pawl 478 will assist in maintaining the plunger in thisappropriate position. In the event that there is subsequent loosening ofthe chain which requires the device to be re-tensioned, this is simplyachieved by again releasing the compression plate 468 by adjustment ofthe appropriate rotatable release mechanism (wing-nut 471) whereby thebiasing force of the coil spring 476 then effects sufficientdisplacement of the support member 460 to automatically re-tension thechain. This re-tensioned chain can then be clamped in position byretightening of the wing nut 471 compression plate 468 as previouslydescribed.

In the event that a user wishes to remove or replace the chain member458 this is simply achieved by releasing the non-return ratchet pawl andapplying sufficient force to the free-end of the support member 460 toovercome the biasing force of the spring 476 to effect sufficientdisplacement of the support member 460 towards the drive wheel 462 toallow the chain to be removed from such support member 460.

However, this specific embodiment provides an enhanced and simplifiedmeans of self-adjusting tensioning of a chain about a support memberwhich simply allows loosening of the appropriate wing-nut on thecompression plate 468 to effect appropriate self-adjustment of the chaintension.

Basically, this self adjusting blade tensioning device 450 effectsrelative displacement between the two support wheels 464 and 462 asshown. This is achieved by mounting the driveable support wheel 464 onthe support member 460 and securing the tensioning device 450 so as tobe immovably displaced relative to the driven support wheel 462.

It is to be appreciated that this specific feature of self-adjustingblade tensioning device is not limited to use with a shear arrangementof the embodiments of FIGS. 1 to 7 but is equally applicable to anydevice utilising a rotatable chain where a minimum tensioning of thechain is required to be maintained and regularly adjusted, for example,conventional chainsaws or even bicycles. In addition, whilst the use ofa wheel-nut is envisaged being mounted on a conventional screw threadedmember to effect adjustment of the compression plate 468, alternativemeans of adjustment of this compression plate 468 to and away from themounting block 466 is readily envisaged and could simply be aconventional nut mounted on a screw threaded member or even a hydrauliccompression arrangement.

FIGS. 11 to 14 show a further embodiment of the present invention, inwhich parts common to the embodiment of FIGS. 1 to 7 are denoted by likereference numerals but increased by 100. The vegetation pruning device102 has a main body 103, formed from a pair of mating clamshells 103 a,103 b, from which a first handle 114 extends and is formed integrally. Asecond handle 116 is pivotable relative to the body 103, and the mainbody 103 supports drive sprocket 130 which is mounted to an output shaftof the motor (not shown) which is received in a cavity 105 (FIG. 13) inthe body 103 such that the output shaft of the motor is arrangedgenerally coaxially with the point at which the handles 114, 116 pivotrelative to each other. This minimises the extent to which the motor,which is generally the heaviest component of the device 102, moves asthe handles 114, 166 are moved relative to each other, making the device102 easier to use.

A pair of arms 104, 106 are arranged such that their distal ends 104 a,106 a touch each other when the handles 114, 116 are in the closedposition, and the arm 104 is pivotably mounted to the body 103 aboutaxis 160. The arm 104 carries a guard 162 (FIG. 12) having a pair ofcurved upper surfaces 164 provided with a series of teeth 166 defined bynotches 168. As shown in greater detail in FIGS. 13 and 14, the arm 104is integral with a first gear segment 170 located within the body 103and which meshes with corresponding second gear segment 172 formedintegrally with the handle 116 which is movable relative to the body103. In this way, as the handles 114, 116 pivot relative to each other,movement of the first gear segment 170 causes movement of the secondgear segment 172, as a result of which the guard 162 pivots relative tothe cutting chain 108 (FIG. 12) to grip vegetation between the guard andthe cutting chain. The teeth 166 on the guard 162 counteract thetendency of the cutting chain 108 to cause logs gripped between theguard 162 and the chain 108 to rotate, and the curved upper surfaces 164of the guard 162 prevent logs from becoming jammed between the guard 162and the chain 108.

The radii of the first and second gear segments 170, 172 are chosen suchthat the angle of movement between the guard 162 and the cutting chain108 is larger than the angle of movement between the handles 114, 116.This achieves the advantage of reducing the gripping force between theguard 162 and the chain 108 for a given force applied between thehandles 114, 116, which results in less electric current being drawn bythe motor. This provides the advantage of enabling a motor of lowerpower (and therefore less weight) to be used, as well as reducing wearon the guard 162 and chain 108, and enabling a user to reach further bymeans of the tool, since the user's hands can be closer together Inaddition, by causing the distal ends 104 a, 106 a of arms 104, 106 tomeet when the handles 114, 116 are in the closed position relative toeach other, this further enhances the safety of the device 102 byminimising the risk of inadvertent contact between power supply cable138 and chain 108.

It will be appreciated by persons skilled in the art that the aboveembodiments have been described by way of example only and not in anylimitative sense, and that various alterations and modifications arepossible without departure from the scope of the invention as defined bythe appended claims.

For example, the arms 4, 6 can be arranged to control access to chain 8to enhance the safety of the apparatus, for example by biasing the arms4, 6 towards their closed position by means of one or more springs,and/or by having an openable guard on one of the arms 4, 6 to allowaccess to the chain 8 to enable the chain 8 to be replaced when itbecomes worn. An interlock arrangement can prevent the guard from beingopened when the motor 36 is actuated and/or when the arms 4, 6 are intheir open position relative to each other offering access to thecutting element 8, and can prevent the motor from being actuated whenthe guard is open. Also, it will be appreciated that the cutting elementcan be driven in a number of ways, for example by means of motor 36having an output shaft arranged generally parallel to the axis ofrotation of sprocket wheels driving the cutting element, or generallyperpendicular to such axes, rotation of the output shaft of motor 36driving one of the sprockets by means of one of more conical gears, or agear plate rotated about an axis perpendicular to the axis of the outputshaft and having gear teeth on its end face. One or more of the arms 4,6 can also be arranged to have cutting edges on the face thereof facingaway from the cutting element 8, so that the cutting edges can be usedto effect manual cutting of vegetation by means of opening of the arms4, 6 relative to each other.

1. A vegetation pruning device comprising: a pair of arms adapted topivot relative to each other about an axis to adjust the angle betweensaid arms, wherein each said arm has at least one respective handleportion adapted to be gripped by a user; a motor having a rotary outputdrive; an endless flexible cutting element mounted to a support andadapted to be driven relative to said support by means of said rotaryoutput drive to cut vegetation presented thereto; at least one grippingmember adapted to be moved relative to said cutting element by means ofpivoting said arms relative to each other to grip vegetation betweensaid gripping member and said cutting element; and a gear mechanismconnected between at least one said gripping member and at least onesaid arm, wherein pivoting of said arms through a first angle relativeto each other causes pivoting of said gripping member and said supportthrough a second angle, larger than said first angle, relative to eachother.
 2. A vegetation pruning device according to claim 1, wherein thegear mechanism comprises at least one first gear element mounted to asaid arm and at least one second gear element mounted to a said grippingmember and engaging a said first gear element.
 3. A vegetation pruningdevice according to claim 2, wherein at least one first gear elementand/or at least one said second gear element comprises a respectivesegment of a respective gear wheel corresponding to pivoting movement ofsaid arms through less than 180 degrees.
 4. A vegetation pruning deviceaccording to claim 1, wherein at least one said gripping member isprovided with at least one protrusion for resisting rotation ofvegetation gripped between said gripping member and said cutting elementrelative to said gripping member.
 5. A vegetation pruning deviceaccording to claim 1, wherein at least one said gripping member has atleast one respective curved edge facing towards said cutting element. 6.A vegetation pruning device according to claim 4, wherein at least onesaid protrusion is defined by a respective notch in a said curved edge.7. A vegetation pruning device according to claim 1, wherein at leastone said gripping member is pivotably mounted relative to one of saidarms.
 8. A vegetation pruning device according to claim 1, wherein saidmotor is mounted to a first said arm.
 9. A vegetation pruning deviceaccording to claim 8, further comprising at least one power supply forpowering said motor, wherein at least one said power supply is mountedto said first arm on a side therefore opposite to said motor.
 10. Avegetation pruning device according to claim 1, wherein the arms arepivotable between a first position allowing access to said cuttingelement, and a second position in which the cutting element issubstantially inaccessible.
 11. A vegetation pruning device according toclaim 10, further comprising first biasing means for biasing said armstowards said second position.
 12. A vegetation pruning device accordingto claim 10, wherein a said gripping member is provided on a first saidarm and a guard member is provided on a second said arm.
 13. Avegetation pruning device according to claim 12, wherein said guardmember is moveable between a first position allowing access to saidcutting element and a second position preventing access to said cuttingelement.
 14. A vegetation pruning device according to claim 13, furthercomprising second biasing means for biasing said guard member towardssaid second position.
 15. A vegetation pruning device according to claim13, wherein said guard member is moveable to said first position onlywhen said arms are in said second position.
 16. A vegetation pruningdevice according to claim 12, wherein said gripping member and/or saidguard member is resiliently biased towards the cutting element andmovable away therefrom under application of force.
 17. A vegetationpruning device according to claim 16, wherein said gripping memberand/or said guard member comprises first vegetation restraining meanshaving a series of indentations and or projections disposed towards saidcutting element to provide points of restraint or retention of saidvegetation thereagainst.
 18. A vegetation pruning device according toclaim 16, wherein said gripping member and/or said guard member isassociated with said cutting element so as to be displaceable away fromsaid cutting element by said vegetation through which said cuttingelement has cut.
 19. A vegetation pruning device according to claim 12,wherein said gripping member and said guard member are adapted to engageeach other at least adjacent respective ends thereof remote from saidaxis when said arms are in said second position.
 20. A vegetationpruning device according to claim 12, further comprising a further guardmember for preventing access to said cutting element at an end thereofremote from said axis.
 21. A vegetation pruning device according toclaim 20, wherein said further guard member is adapted to lock saidgripping member and said guard member together when said arms are insaid second position.
 22. A vegetation pruning device according to claim10, further comprising first locking means for releasably locking saidarms in said second position.
 23. A vegetation pruning device accordingto claim 1, wherein a second said arm comprises second vegetationrestraining means for restraining vegetation inserted between said pairof arms from displacement when engaged with said cutting element.
 24. Avegetation pruning device according to claim 23, wherein said secondvegetation restraining means comprises a series of indentations and orprojections disposed towards said cutting element to provide points ofrestraint or retention of said vegetation thereagainst.
 25. A vegetationpruning device according to claim 24 wherein said series of projectionscomprises a plurality of teeth inclined and facing towards said cuttingelement.
 26. A vegetation pruning device according to claim 1, whereinsaid second arm comprises a substantially parallel pair of side wallsdefining a channel therebetween for at least partially receiving saidcutting element as the cuffing element is pivotally displaced towardssaid second arm.
 27. A vegetation pruning device according to claim 26,further comprising at least one stop member to limit pivotaldisplacement of said arms towards one another for restraining saidcutting element at a predetermined pivotal position relative to saidsecond arm so as to remain received within said channel.
 28. Avegetation pruning device according to claim 26, wherein said channelcomprises an inner surface extending between said substantially parallelside walls defining a dust/debris conveying path communicating with adust/debris extraction aperture.
 29. A vegetation pruning deviceaccording to claim 26, wherein said substantially parallel pair of sidewalls are profiled to allow at least part of said cutting element topass completely through said channel as said cutting element ispivotally displaced towards said other of said pair of arms.
 30. Avegetation pruning device as claimed in claim 29, wherein said sidewalls have a V-shaped profile for receiving and supporting in an innerapex thereof vegetation to be cut.
 31. A vegetation pruning deviceaccording to claim 1, wherein the motor rotary output drive includes atoothed drive wheel.
 32. A vegetation pruning device according to claim1, wherein said motor has an output gear adapted to rotate about an axissubstantially parallel or substantially perpendicular to the axis ofrotation of said rotary output drive.
 33. A vegetation pruning deviceaccording to claim 1, wherein the cutting element is mounted upon asupport member and arranged for rotation thereabout under the influenceof the rotary output drive.
 34. A vegetation pruning device according toclaim 33, wherein the support member includes a driven and a drive wheelaround which the cutting element moves as the drive wheel rotates.
 35. Avegetation pruning device according to claim 33, wherein the cuttingelement rotates within a first plane and the arms of the pair of armseach include a surface which extends either side of this first plane.36. A vegetation pruning device according to claim 1, wherein thecutting element comprises a chain.
 37. A vegetation pruning deviceaccording to claim 36, wherein the motor rotary output drive includes atoothed drive wheel and wherein the teeth of the toothed wheel fitbetween the links of the chain in use to provide motive force to thechain.
 38. A vegetation pruning device according to claim 36, whereinthe chain further includes a plurality of barbs to assist in vegetationpruning.
 39. A vegetation pruning device according to claim 1, furthercomprising an actuator for controlling operation of the motor.
 40. Avegetation pruning device according to claim 39, wherein the actuator isa variable speed-controller for governing the output speed of the motor.41. A vegetation pruning device according to claim 39, wherein saidactuator comprises at least one resiliently biased switch member mountedon each of the two arm members, wherein said actuator is restrained fromoperating said motor unless at least one said switch member on each armis operated.
 42. A vegetation pruning device as claimed in claim 33,further comprising a self adjusting tensioning device to allow automaticadjustment of the support member.
 43. A vegetation pruning deviceaccording to claim 42, wherein adjustment of said support member effectstensioning of said cutting element.
 44. A vegetation pruning device asclaimed in claim 42, wherein said self adjusting tensioning devicecomprises adjustable restraint means for releasably securing saidsupport member relative to said pruning device together with a rigidsupport block rigidly secured to one of said pair of pivotally coupledarms on which said support member is mounted, said block having aresiliently biased adjustment member disposed between said support blockand said support member to exert a displacement force on said supportmember away from said support block when said restraint member is in areleased position.
 45. A vegetation pruning device as claimed in claim44, wherein said biasing member comprises a spring biased plunger havinga first ratchet member and said support block having a second ratchetmember whereby engagement between said first and second ratchet membersprevents displacement of said plunger towards said support block.
 46. Avegetation pruning device according to claim 1, further comprising alubricating device for depositing lubricating material on said cuttingelement.
 47. A vegetation pruning device according to claim 46, whereinsaid lubricating device includes a reservoir for lubricating materiallocated within a second said arm.
 48. A vegetation pruning deviceaccording to claim 46, wherein said lubricating device is adapted todeposit a predetermined amount of lubricating material on said cuttingelement in response to opening of said arms relative to each otherand/or opening and closing of said arms relative to each other.
 49. Avegetation pruning device according to claim 1, wherein said motor is anelectric motor adapted to be switched so as to effect braking of saidcutting element.